There are four major characters in the play: Calisto, Sempronio, Melibea, and Celestina. Calisto is a young man of twenty-three. He has fallen in love with a young woman named Melibea, who is, evidently, quite beautiful. He is very romantic but also quite melodramatic in his descriptions of her beauty and the misery he feels at her refusal. He tells Sempronio, his servant,

My will is not obedient to reason and I harbor in my breast peace and war, love and hate, injuries and suspicions. And all of these from one and the same cause.

It even seems as though his unrequited feelings will make him physically ill. Melibea seems to think that Calisto’s feelings for her are "illicit" ones—in other words, that he only likes her for her beauty and wants to sleep with her. Calisto trusts Sempronio completely, so when Sempronio offers to enlist the aid of Celestina, an old brothel owner (and well-known woman of disrepute), to help get Melibea to fall in love with Calisto, Calisto immediately accepts his idea. However, when Sempronio goes to meet with Celestina, it becomes clear that the servant and Celestina know each other quite well. They agree to work together to try to get as much money as they can from Calisto, which they will split between them.

Celestina successfully manipulates Melibea into falling in love with Calisto, but when she makes excuses to avoid sharing her payment with Sempronio and Parmeno (another servant of Calisto’s whom Celestina and Sempronio have persuaded to help them), they kill her. Minor characters include Sosia, another of Calisto’s servants; Elicia and Areusa, both prostitutes who work for Celestina and plot against Calisto and Melibea after the deaths of Celestina, Sempronio, and Parmeno; as well as Pleberio, Melibea’s father.